Re: [Bluez-devel] TPL (transmit power level)

Steven Singer
2005-02-22T16:59:33Z

Flávio wrote:
> One more question about this topic.
> In bluetooth core says that the range of the tpl (transmit power
> level) is between -30<= N<=20 and the step (resolution) is one
> unit,

Where does it say that the step is one unit? It might say that the
units for this value are dBm.

> but when i execute the command hci_read_tpl (transmit power
> level) all the values that i receive are:
> 17 ; 14 ; 10 ; 6 ; 2 ; -2 ; -6 ; -9 and no more :(
> why?

This is completely as expected.

If you look right at the start of the Bluetooth spec in the radio
specification under transmitter characteristics, it says:

The power steps shall form a monotonic sequence with a maximum
step size of 8 dB amd a minimum step size of 2 dB.

The easiest way for a manufacturer to meet this specification is with
a preprogrammed set of levels.

A device isn't obliged to use the full range. The radio spec also says:

Power control capability under +4 dBm is optional.

Your chip appears to go down to -9 dBm which exceeds the spec.

> it´s something about Bluez or is the Firmware (of my dongle usb)
> that realy gives that values for tpl?

The firmware of the dongle reports the values.

Tour device is completely within spec.

- Steven
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